Electro immersion lacquer produced by melt emulsification

ABSTRACT

Novel electrodeposition coating material preparable by (i) melting at least one self-crosslinking binder, or (ii) separately melting at least one externally crosslinking binder and at least one crosslinking agent and supplying the melts to a mixing unit in which the melts are homogenized, introducing the resultant melt into an aqueous medium, and emulsifying it therein; and the use of the novel electrodeposition coating material to coat electrically conductive substrates.

[0001] The present invention relates to a novel electrodepositioncoating material preparable by melt emulsification. The presentinvention further relates to a novel process for preparing the novelelectrodeposition coating material. The present invention relates notleast to the use of the novel electrodeposition coating materials tocoat electrically conductive substrates.

[0002] In the preparation of electrodeposition coating materials it iscommon to employ organic solvents in order to reduce the viscosity ofthe binders and/or of the crosslinking agents, in order that they may bedispersed more readily at low temperatures in the aqueous media. Adisadvantage of this process is the need to remove the organic solventsfrom the electrodeposition coating materials subsequently by means ofdistillation.

[0003] For reasons of environmental protection and of cost, however,attempts are being made to forego the use of solvents. In particular,the distillation process is time-consuming and, moreover, presentssafety problems.

[0004] If no organic solvents are used in preparing electrodepositioncoating materials, the viscosity of the binders and/or of thecrosslinking agents must be lowered by increasing their temperature inorder to facilitate, or indeed enable, their dispersion. The hightemperatures, however, prevent the introduction even of crosslinkingagents of very low reactivity, since unwanted premature crosslinkingreactions occur with the binders. The introduction of reactivecrosslinking agents as commonly used for so-called low-bake applicationsis then completely impossible.

[0005] Similar problems also occur when using self-crosslinking binders.

[0006] It is an object of the present invention to find a newelectrodeposition coating material from which the disadvantages of theprior art are now absent and which instead may be prepared at leastusing a smaller amount of organic solvent than is usually required forthe electrodeposition coating materials of the prior art, preferablywithout organic solvents, without premature crosslinking of theconstituents of the electrodeposition coating material. This should alsobe reliably so even when using highly reactive crosslinking agents orhighly reactive self-crosslinking binders. Moreover, the newelectrodeposition coating materials should have the same advantageousprofile of properties as their prior art counterparts, if not indeedexceeding them.

[0007] Accordingly, we have found the novel electrodeposition coatingmaterial which is preparable by

[0008] (i) melting at least one self-crosslinking binder, or

[0009] (ii) separately melting at least one externally crosslinkingbinder and at least one crosslinking agent and supplying the melts to amixing unit in which the melts are homogenized,

[0010] introducing the resultant melt into an aqueous medium, andemulsifying it therein.

[0011] In the text below, the novel electrodeposition coating materialis referred to as the “electrodeposition coating material of theinvention”.

[0012] Additional subject-matter of the invention will emerge from thedescription.

[0013] The electrodeposition coating material of the invention comprisesat least one self-crosslinking binder.

[0014] In the context of the present invention, the term“self-crosslinking” refers to the ability of a binder (regarding thatterm cf. Römpp Lexikon Lacke und Druckfarben, Georg Thieme Verlag,Stuttgart, New York, 1998, “Binders”, pages 73 and 74) to enter intocrosslinking reactions with itself. This requires that the binderscontain complementary reactive functional groups which react with oneanother and so lead to crosslinking. Or else the binders containreactive functional groups which react “with themselves”.

[0015] Or else the electrodeposition coating material of the inventioncomprises at least one external crosslinking binder and at least onecrosslinking agent.

[0016] Binders are termed externally crosslinking if they contain onekind of the complementary reactive functional groups and the other kindis provided by a curing agent, hardener, or crosslinking agent. Forfurther details, reference is made to Römpp Lexikon Lacke undDruckfarben, Georg Thieme Verlag, Stuttgart, New York, 1998, “Curing”,pages 274 to 276, especially page 275, bottom.

[0017] Suitable reactive functional groups of the binders are preferablythio, amino, hydroxyl, carbamate, allophanate, carboxyl and/or(meth)acrylate groups, but especially hydroxyl groups, and suitablecomplementary functional reactive groups of the crosslinking agents arepreferably anhydride, carboxyl, epoxy, blocked isocyanate, urethane,methylol, methylol ether, amino, hydroxyl and/or beta-hydroxyalkylamidegroups, but especially blocked isocyanate groups.

[0018] In the self-crosslinking binders, in contrast, both types ofcomplementary reactive functional groups are present, preferablyhydroxyl groups and blocked isocyanate groups, and/or reactivefunctional groups which are able to react “with themselves”, such asmethylol ether groups, for example.

[0019] In accordance with the invention, the externally crosslinkingbinders are of advantage and are therefore used with preference.

[0020] In order that the binders may be dispersed in water andelectrophoretically deposited, they contain functional groups which areionic or are convertible to ionic groups.

[0021] These groups comprise

[0022] (a) functional groups convertible to cations by neutralizingagents and/or quaternizing agents, and/or cationic groups, or

[0023] (b) functional groups convertible to anions by neutralizingagents, and/or anionic groups.

[0024] The binders with functional groups (a) are used in cathodicallydepositable (cathodic) electrodeposition coating materials of theinvention, whereas the binders with functional groups (b) are employedin anodically depositable (anodic) electrodeposition coating materialsof the invention.

[0025] Examples of suitable functional groups (a) for use in accordancewith the invention, which are convertible to cations by neutralizingagents and/or quaternizing agents, are primary, secondary or tertiaryamino groups, second sulfide groups or tertiary phosphine groups,especially tertiary amino groups or secondary sulfide groups.

[0026] Examples of suitable cationic groups (a) for use in accordancewith the invention are primary, secondary, tertiary or quaternaryammonium groups, tertiary sulfonium groups or quaternary phosphoniumgroups, preferably quaternary ammonium groups of tertiary sulfoniumgroups, but especially quaternary ammonium groups.

[0027] Examples of suitable functional groups (b) for use in accordancewith the invention, which are convertible to anions by neutralizingagents, are carboxylic acid, sulfonic acid or phosphonic acid groups,especially carboxylic acid groups.

[0028] Examples of suitable anionic groups (b) for use in accordancewith the invention are carboxylate, sulfonate or phosphonate groups,especially carboxylate groups.

[0029] The selection of the groups (a) or (b) is to be made so as torule out the possibility of disruptive reactions with theabove-described complementary reactive functional groups. The skilledworker will therefore be able to make the selection in a simple manneron the basis of his or her art knowledge.

[0030] Examples of suitable neutralizing agents for functional groups(a) convertible to cations are organic and inorganic acids such assulfuric acid, amidosulfuric acid (amidosulfonic acid), C₁-C₁₀ sulfonicacids such as methanesulfonic acid or hexanesulfonic acid, hydrochloricacid, phosphoric acid, formic acid, acetic acid, lactic acid,dimethylolpropionic acid or citric acid, especially formic acid, aceticacid or lactic acid.

[0031] Examples of suitable neutralizing agents for functional groups(b) convertible to anions are ammonia, ammonium salts such as ammoniumcarbonate or ammonium hydrogen-carbonate, for example, and also amines,such as trimethylamine, triethylamine, tributylamine, dimethyl-aniline,diethylaniline, triphenylamine, dimethyl-ethanolamine,diethylethanolamine, methyldiethanol-amine, triethanolamine and thelike, for example.

[0032] In general, the amount of neutralizing agent is chosen so thatfrom 1 to 100 equivalents, preferably from 30 to 90 equivalents, of thefunctional groups (a) or (b) of the binder are neutralized.

[0033] Examples of suitable binders for anodic electro-depositioncoating materials of the invention are disclosed in the patent DE-A 2824 418. These are preferably polyesters, epoxy resin esters,poly(meth)acrylates, maleate oils or polybutadiene oils having aweight-average molecular weight of from 300 to 20,000 daltons and anacid number of from 35 to 300 mg KOH/g.

[0034] Examples of suitable binders for cathodic electro-depositioncoating materials of the invention are disclosed in the patentapplications EP 0 004 090 A 1, EP 0 059 895 A 1, EP 0 012 463 A 1, EP 0082 291 A 1, EP 0 234 395 A 1, EP 0 227 975 A 1, EP 0 178 531 A 1, EP 0333 327 A 1, EP 0 310 971 A 1, EP 0 456 270 A 1, U.S. Pat. Nos.3,799,854 A 1, 3,948,299 A 1, 3,922,253 A 1, 4,031,050 A 1, 4,252,703 A1, 03 4,332,711 A 1, EP 0 261 385 A 1, EP 0 245 786 A 1, DE 27 01 002 A1, DE 31 03 642 A 1, DE 31 08 073 A 1, DE 33 24 211 A 1, EP 0 414 199 A1, EP 0 476 514 A 1, EP 0 640 700 A 1 and WO 98/33835. These arepreferably resins (A) containing primary, secondary, tertiary orquaternary amino or ammonium groups and/or tertiary sulfonium groups andhaving amine numbers of preferably between 20 and 250 mg KOH/g and aweight-average molecular weight of preferably from 300 to 20,000daltons. Use is made in particular of amino (meth)acrylate resins, aminoepoxy resins, amino epoxy resins having terminal double bonds, aminoepoxy resins having primary and/or secondary hydroxyl groups, aminopolyurethane resins, amino-containing polybutadiene resins, or modifiedepoxy resin-carbon dioxide-amine reaction products.

[0035] The amount of the above-described binders in theelectrodeposition coating materials of the invention may vary verywidely.

[0036] In the case of the self-crosslinking binders, it may be up to100% by weight, based on the solids of the electrodeposition coatingmaterial of the invention.

[0037] In the case of the externally crosslinking binders, it ispreferably from 40 to 95, more preferably from 50 to 90, and inparticular from 55 to 85% by weight, based in each case on the solids ofthe electrodeposition coating material of the invention.

[0038] In the context of the present invention, the “solids” is thatfraction of the electrodeposition coating material of the invention thatforms the electrodeposition coating following the thermal curing of theelectrophoretically deposited coating film.

[0039] Preference is given to the use of cathodic electrodepositioncoating materials of the invention.

[0040] Preferably, the electrodeposition coating materials of theinvention comprise crosslinking agents.

[0041] Examples of suitable crosslinking agents are blocked organicpolyisocyanates, especially blocked polyisocyanates known as paintpolyisocyanates, having blocked isocyanate groups attached to aliphatic,cycloaliphatic, araliphatic and/or aromatic moieties.

[0042] They are preferably prepared using polyisocyanates having 2 to 5isocyanate groups per molecule and having viscosities of from 100 to10,000, preferably from 100 to 5000, and in particular from 100 to 2000mPas (at 23° C.). Furthermore, the polyisocyanates may have beenhydrophilically or hydrophobically modified by conventional means.

[0043] Examples of suitable polyisocyanates are described, for example,in “Methoden der organischen Chemie” [Methods of organic chemistry],Houben-Weyl, volume 14/2, 4^(th) edition, Georg Thieme Verlag, Stuttgart1963, pages 61 to 70, and by W. Siefken, Liebigs Annalen der Chemie,volume 562, pages 75 to 136.

[0044] Further examples of suitable polyisocyanates are polyisocyanatescontaining isocyanurate, biuret, allophanate, iminooxadiazinedione,urethane, urea and/or uretdione groups. Polyisocyanates containingurethane groups, for example, are obtained by reacting some of theisocyanate groups with polyols, such as trimethylolpropane and glycerol,for example. It is preferred to use aliphatic or cycloaliphaticpolyisocyanates, especially dimerized and trimerized hexamethylenediisocyanate, isophorone diisocyanate, 2-isocyanatopropylcyclohexylisocyanate, dicyclohexylmethane 2,4′-diisocyanate, dicyclohexylmethane4,4′-diisocyanate or 1,3-bis(isocyanatomethyl)cyclohexane (BIC),diisocyanates derived from dimeric fatty acids, as marketed under thecommercial designation DDI 1410 by Henkel,1,8-diisocyanato-4-isocyanatomethyloctane,1,7-diisocyanato-4-isocyanatomethylheptane and/or1-isocyanato-2-(3-isocyanatopropyl)cyclohexane.

[0045] Examples of suitable blocking agents for preparing the blockedpolyisocyanates are the blocking agents known from U.S. Pat. No.4,444,954, such as

[0046] i) phenols such as phenol, cresol, xylenol, nitro-phenol,chlorophenol, ethylphenol, t-butylphenol, hydroxybenzoid acid, esters ofthis acid, or 2,5-di-tert-butyl-4-hydroxytoluene;

[0047] ii) lactams, such as ε-caprolactam, δ-valerolactam,γ-butyrolactam or β-propiolactam;

[0048] iii) active methylenic compounds, such as diethyl malonate,dimethylmalonate, ethyl or methyl acetoacetate or acetylactone;

[0049] iv) alcohols such as methanol, ethanol, n-propanol, isopropanol,n-butanol, isobutanol, t-butanol, n-amyl alcohol, t-amyl alcohol, laurylalcohol, ethylene glycol monomethyl ether, ethylene glycol monoethylether, ethylene glycol monopropyl ether, ethylene glycol monobutylether, diethylene glycol monomethyl ether, diethylene glycol monoethylether, propylene glycol monomethyl ether, methoxymethanol, glycolicacid, glycolic esters, lactic acid, lactic esters, methylolurea,methylolmelamine, diacetone alcohol, ethylenechlorohydrin,ethylenebromohydrin, 1,3-dichloro-2-propanol, 1,4-cyclohexyldimethanol,trimethylolpropane or acetocyanohydrin;

[0050] v) mercaptans such as butyl mercaptan, hexyl mercaptan, t-butylmercaptan, t-dodecyl mercaptan, 2-mercaptobenzothiazole, thiophenol,methylthiophenol or ethylthiophenol;

[0051] vi) acid amides such as acetoanilide, acetoanisidinamide,acrylamide, methacrylamide, acetamide, stearamide or benzamide;

[0052] vii) imides such as succinimide, phthalimide or maleimide;

[0053] viii)amines such as diphenylamine, phenylnaphthylamine, xylidine,N-phenylxylidine, carbazole, aniline, naphthylamine, butylamine,dibutylamine or butylphenylamine;

[0054] ix) imidazoles such as imidazole or 2-ethylimidazole;

[0055] x) ureas such as urea, thiourea, ethyleneurea, ethylenethioureaor 1,3-diphenylurea;

[0056] xi) carbamates such as phenyl N-phenylcarbamate or 2-oxazolidone;

[0057] xii) imines such as ethylenimine;

[0058] xiii)oximes such as acetone oxime, formaldoxime, acetaldoxime,acetoxime, methyl ethyl ketoxime, diisobutyl ketoxime, diacetylmonoxime, benzophenone oxime or chlorohexanone oximes;

[0059] xiv) salts of sulfurous acid such as sodium bisulfite orpotassium bisulfite;

[0060] xv) hydroxamic esters such as benzyl methacrylohydroxamate (BMH)or allyl methacrylohydroxamate; or

[0061] xvi) substituted pyrazoles, imidazoles or triazoles; and

[0062] xvii)mixtures of these blocking agents, especiallydimethylpyrazole and triazoles, malonic esters and acetoacetic esters,dimethylpyrazole and succinimide, or ethylene glycol monopropyl etherand trimethylolpropane.

[0063] Further examples of suitable crosslinking agents are all knownaliphatic and/or cycloaliphatic and/or aromatic polyepoxides, based forexample on bisphenol A or bisphenol F. Examples of further suitablepolyepoxides are the polyepoxides available commercially under thedesignations Epikote® from Shell, Denacol® from Nagase Chemicals Ltd.,Japan, such as, for example, Denacol EX-411 (pentaerythritolpolyglycidyl ether), Denacol EX-321 (trimethylolpropane polyglycidylether), Denacol EX-512 (polyglycerol polyglycidyl ether) and DenacolEX-521 (polyglycerol polyglycidyl ether).

[0064] As crosslinking agents it is also possible to usetris(alkoxycarbonylamino)triazines (TACT) of the general formula

[0065] Examples of suitable tris(alkoxycarbonylamino)triazines (B) aredescribed in the patents U.S. Pat. No. 4,949,213 A 1, U.S. Pat. No.5,084,541 A 1, and EP 0 624 577 A 1. In particular, the tris(methoxy-,tris(butoxy- and/or tris(2-ethylhexoxycarbonylamino)triazines are used.

[0066] Of advantage are the methyl butyl mixed esters, thebutyl-2-ethylhexyl mixed esters, and the butyl esters. These have theadvantage over the straight methyl ester of improved solubility inpolymer melts, and also tend less toward crystallizing out.

[0067] Further examples of suitable crosslinking agents are aminoresins, examples being melamine, guanamine, benzoguanamine or urearesins. Also suitable are the conventional amino resins some of whosemethylol and/or methoxymethyl groups have been defunctionalized usingcarbamate or allophanate groups. Crosslinking agents of this kind aredescribed in the patents U.S. Pat. No. 4,710,542 A 1 and EP 0 245 700 B1 and also in the article by B. Singh and coworkers, “CarbamylmethylatedMelamines, Novel Crosslinkers for the Coatings Industry” in AdvancedOrganic Coatings Science and Technology Series, 1991, volume 13, pages193 to 207.

[0068] Further examples of suitable crosslinking agents arebeta-hydroxyalkylamides such asN,N,N′,N′-tetrakis(2-hydroxyethyl)adipamide orN,N,N′,N′-tetrakis(2-hydroxypropyl)adipamide.

[0069] Further examples of suitable crosslinking agents are compoundshaving on average at least two groups capable of transesterification,examples being reaction products of malonic diesters and polyisocyanatesor of esters and partial esters of polyhydric alcohols of malonic acidwith monoisocyanates, as described in European Patent Application EP 0596 460 A 1.

[0070] Particular preference is given to the use of the blockpolyisocyanates.

[0071] The amount of the crosslinking agents in the electrodepositioncoating materials of the invention may vary widely and is guided inparticular first by the functionality of the crosslinking agents andsecond by the number of complementary reactive functional groups presentin the binder, and also by the target crosslinking density. The skilledworker will therefore be able to determine the amount of thecrosslinking agents on the basis of his or her general art knowledge,possibly with the aid of simple rangefinding tests. Advantageously, thecrosslinking agent is present in the electrodeposition coating materialof the invention in an amount of from 5 to 60% by weight, withparticular preference from 10 to 50% by weight, and in particular from15 to 45% by weight, based in each case on the solids of theelectrodeposition coating material of the invention. It is advisable inthis context, moreover, to choose the amounts of crosslinking agent andbinder such that in the electrodeposition coating materials of theinvention the ratio of reactive functional groups in the crosslinkingagent to complementary reactive functional groups in the binder is from2:1 to 1:2, preferably from 1.5:1 to 1:1.5, with particular preferencefrom 1.2:1 to 1:1.2, and in particular from 1.1:1 to 1:1.1.

[0072] The electrodeposition coating material of the invention maycomprise customary coating additives in effective amounts. Examples ofsuitable additives are

[0073] organic and/or inorganic pigments, anticorrosion pigments and/orfillers such as calcium sulfate, barium sulfate, silicates such as talcor kaolin, silicas, oxides such as aluminum hydroxide or magnesiumhydroxide, nanoparticles, organic fillers such as textile fibers,cellulose fibers, polyethylene fibers or wood flour, titanium dioxide,carbon black, iron oxide, zinc phosphate or lead silicate; theseadditives may also be incorporated into the electrodeposition coatingmaterials of the invention by way of pigment pastes, suitable dispersingresins being the binders described above;

[0074] anticrater agents, as described in European Patent Application EP0 301 293 A 1;

[0075] water-soluble polymers such as polyvinyl alcohols orwater-soluble cellulose ethers, as disclosed in European PatentApplication 0 640 700 A 1;

[0076] free-radical scavengers;

[0077] organic corrosion inhibitors;

[0078] crosslinking catalysts such as organic and inorganic salts andcomplexes of tin, of lead, of antimony, of bismuth, of iron or ofmanganese, preferably organic salts and complexes of bismuth and of tin,especially bismuth lactate, ethylhexanoate or dimethylolpropionate,bismuth-amino acid complexes, dibutyltin oxide or dibutyltin dilaurateor dioleate;

[0079] slip additives;

[0080] polymerization inhibitors;

[0081] defoamers;

[0082] emulsifiers, especially nonionic emulsifiers such as alkoxylatedalkanols, polyols, phenols and alkylphenols or anionic emulsifiers suchas alkali metal salts or ammonium salts of alkanecarboxylic acids,alkanesulfonic acids, and sulfo acids of alkoxylated alkanols, polyols,phenols and alkylphenols;

[0083] wetting agents such as siloxanes, fluoro compounds, carboxylicmonoesters, phosphoric esters, polyacrylic acids and their copolymers orpolyurethanes;

[0084] adhesion promoters;

[0085] leveling agents;

[0086] film-forming auxiliaries such as cellulose derivatives;

[0087] flame retardants;

[0088] thermally crosslinkable reactive diluents, such as positionallyisomeric diethyloctanediols, hydroxyl-containing hyperbranched compoundsor dendrimers, as described in the patent applications DE 198 09 643 A1, DE 198 40 605 A 1 or DE 198 05 421 A 1; or

[0089] biocides;

[0090] further examples of suitable coatings additives are described inthe textbook “Lackadditive” [Coatings additives] by Johan Bieleman,Wiley-VCH, Weinheim, N.Y. 1998.

[0091] The electrodeposition coating material of the invention ispreparable by the process of the invention.

[0092] In one preferred variant of the process of the invention, atleast one of the above-described self-crosslinking binders is melted,after which the resultant melt is introduced into an aqueous medium andemulsified therein.

[0093] In a particularly preferred variant of the process of theinvention, at least one of the above-described externally crosslinkingbinders and at least one of the above-described crosslinking agents aremelted separately and supplied to a mixing unit in which the melts arehomogenized. The resultant melt is introduced into an aqueous medium andemulsified therein.

[0094] Both the binders and/or the crosslinking agents may comprise atleast one of the above-described additives, provided they do not disruptthe melting operation, through decomposition or chemical reactions, forexample.

[0095] Preferably, the aqueous medium comprises at least one of theabove-described neutralizing agents in amounts sufficient to stablydisperse the above-described binders. Particularly preferredneutralizing agents are the above-described acids. Furthermore, theaqueous medium may comprise at least one of the above-describedadditives.

[0096] The temperatures of the melts may vary widely. Thus, thetemperatures chosen should not be so high that the binders or thecrosslinking agents undergo thermal decomposition and/or prematurecrosslinking. On the other hand, the temperatures ought not to be so lowthat the excessive viscosity of the melts means that they can no longerbe readily mixed with one another and dispersed in the aqueous medium.It is preferred to employ temperatures of between 40 and 160, preferably50 and 140, and in particular 70 and 130° C.

[0097] Mixing units which can be used in connection with the process ofthe invention are all conventional mixing units suitable for thehomogenous mixing of comparatively viscous melts. Examples of suitablemixing units are static mixers of the Sulzer type, marketed by SulzerChemtech GmbH. The melts may be run once or a number of times incirculation through the mixing units. An alternative option is toconnect up at least two mixing units in series.

[0098] To emulsify the melt in water, it is possible in the process ofthe invention to use all conventional equipment as commonly used in theemulsification of liquid or melted substances in water.

[0099] Examples of suitable equipment of this kind include theabove-described static mixers, rotor-stator systems, and high-pressurehomogenizers.

[0100] Examples of suitable rotor-stator systems are high-speed stirrers(Ultraturrax), wet rotor mills, in-line dissolvers, or toothed-wheeldispersing units as described, for example, in European PatentApplication EP 0 648 537 A 1 and marketed under the tradename“K-Generatoren” by Kinematica AG, Lucerne, Switzerland.

[0101] Examples of suitable high-pressure homogenizers are those whichoperate in accordance with the opposed-jet principle, as are described,for example, in European Patent Application EP 0 401 565 A 1.

[0102] In the process of the invention, the melt and the aqueous mediummay be passed once or several times in circulation through one of theabove-described apparatuses. It is also possible, however, to connect upat least two of these apparatuses in series.

[0103] On the emulsification of the melt in the aqueous medium, thediscontinuous phase of the emulsion is formed as droplets. Their averagesize can vary very widely and is guided in particular by the temperatureof the melt, its viscosity, and the shear field prevailing within theapparatus. Preferably, the average droplet size is from 40 to 1000, morepreferably from 60 to 500, and in particular from 70 to 200 nm.

[0104] In the subsequent course of the process of the invention theresultant emulsion is cooled preferably to room temperature by beingpassed, for example, through a cooling unit, in particular a heatexchanger.

[0105] The resultant electrodeposition coating material of the inventionmay be used as it is for electrophoretic deposition. Preferably, it isdiluted further with water so as to give, preferably, a solids contentof from 5 to 60, with particular preference from 6 to 55, and inparticular from 7 to 50% by weight, based in each case on the solids ofthe electrodeposition coating material of the invention.

[0106] Furthermore, there may be added to the electrodeposition coatingmaterial of the invention at least one of the above-described additives,preferably at least one pigment and/or filler, especially in the form ofat least one pigment paste.

[0107] The process of the invention described above may be conductedcontinuously or batchwise.

[0108] The electrodeposition coating material of the invention may beapplied to substrates by means of a very wide variety of applicationtechniques. In accordance with the invention, however, it is ofadvantage to deposit it electrophoretically onto electrically conductivesubstrates such as motor vehicle bodies or parts thereof.

[0109] For this purpose, the electrically conductive substrate isimmersed in an electrodeposition bath of the invention, in accordancewith the above remarks, the substrate is connected as the cathode oranode, preferably the cathode, a film is deposited on the substrate bymeans of direct current, the coated substrate is removed from theelectrodeposition bath, and the electrodeposited coating film is eitherbaked or just dried.

[0110] The baked electrodeposition coating may subsequently be furthercoated with a surfacer or with an antistonechip coat and a solid-colortopcoat or, alternatively, with a basecoat and a clearcoat. Thereafter,the surface or film or the antistonechip film and the solid-colortopcoat film are normally baked separately, whereas the basecoat and theclearcoat are preferably applied by the wet-on-wet technique and theresulting basecoat film and clearcoat film are baked together.

[0111] The dried electrodeposition coating film may be coated wet-on-wetwith a surfacer or antistonechip coat or a basecoat, after which theelectrodeposition coating film and the surface or film or antistonechipfilm or the basecoat film are baked together (cf. European PatentApplication EP 0 817 614 A 1).

[0112] The resultant electrodeposition coatings of the invention exhibitexcellent throw, outstanding edge protection, and, if any, only a verysmall number of surface defects such as craters. The adhesion of theelectrodeposition coatings to the substrate and to the surfacer coatingsor antistonechip primer coats or basecoats is excellent. Owing to theexcellent smooth surface of the electrodeposition coatings of theinvention, the overlying coatings also have a particularly good,defect-free surface.

[0113] The resultant multicoat color and/or effect finishes of theinvention exhibit an excellent profile of properties, and so may also beused with advantage in the especially demanding technical field ofautomotive OEM finishing.

EXAMPLES Preparation Example 1 The Preparation of a Crosslinking Agentfor Use in Accordance with the Invention

[0114] A reactor equipped with reflux condenser, internal thermometer,and inert gas inlet was charged with 810 parts by weight of isomers andhigher-functionality oligomers based on 4,4′-diphenylmethanediisocyanate, having an isocyanate equivalent weight of 135 (Basonat® A270 from BASF Aktiengesellschaft), under a nitrogen atmosphere. 0.6 partby weight of dibutyltin dilaurate was added and 988 parts by weight ofbutyl diglycol were added dropwise, with stirring, at a rate such thatthe temperature of the reaction mixture remained below 60° C. Followingthe addition, the reaction mixture was held at 100° C. for two hours.Thereafter, no free isocyanate groups were detectable. The resultantblocked polyisocyanate was admixed to 87 parts by weight ofphenoxypropanol and 87 parts by weight of butoxypropanol and cooled to70° C. The solids content was 90%.

Preparation Example 2 The Preparation of a Binder for Use in Accordancewith the Invention

[0115] A reactor equipped with reflux condenser, internal thermometerand inert gas inlet was charged with 1177 parts by weight of acommercial epoxy resin based on bisphenol A, having an epoxideequivalent weight of 188, 92 parts by weight of phenol, 268 parts byweight of bisphenol A and 46 parts by weight of butoxypropanol and thisinitial charge was heated to 130° C. under nitrogen and with stirring.Thereafter, 1.5 parts by weight of triphenylphosphine were added withstirring, whereupon there was an exothermic reaction and the temperaturerose to 155° C. The reaction mixture was subsequently cooled to 130° C.and the epoxide equivalent weight was measured. The target value wasfrom 520 to 530. When this value had been reached, 160 parts by weightof a commercial polyalkylene glycol (Pluriol® P 600 from BASFAktiengesellschaft) were added with cooling. When the temperaturereached 95° C., 113 parts by weight of diethanolamine were added,whereupon there was an exothermic reaction and the temperature rose to115° C. After a further 40 minutes at 115° C., 55 parts by weight ofN,N-dimethylaminopropylamine were added. At this point the temperaturerose briefly to 140° C. Subsequently, the reaction mixture was left tocontinue reacting for two hours at 130° C. until its viscosity remainedconstant. The solids content of the reaction mixture was 97.5%.

Preparation Example 3 The Preparation of an Aqueous Medium

[0116] 2024 parts by weight of deionized water and 41 parts by weight ofan 85% strength aqueous formic acid solution were mixed with one anotherin a preparation vessel.

Preparation Example 4 The Preparation of a Pigment Paste

[0117] The pigment paste was prepared as described in InternationalPatent Application WO 98/33835, page 22, line 23 to page 23, line 30, 3.Cationic, water-soluble dispersing resins, 3.1. Dispersing resin A,Table 1: aqueous pigment pastes, pigment paste B.

Example 1 The Preparation of an Electrodeposition Coating Material ofthe Invention by Melt Emulsification

[0118] Example 1 was conducted using

[0119] 888 parts by weight of the crosslinking agent of PreparationExample 1,

[0120] 1913 parts by weight of the epoxy resin of Preparation Example 2,and

[0121] 2065 parts by weight of the aqueous medium of Preparation Example3.

[0122] The epoxy resin and the crosslinking agent were heated separatelyto 100° C., and melted. Using separate pumps, the epoxy resin melt andthe crosslinking agent melt in a weight ratio of 68.3:31.7 were conveyeduniformly through a static mixer and so homogenized. The static mixerused was a mixer of the Sulzer SMX type. The resultant melt was run intothe aqueous medium, heated to 23° C., and divided therein into finedroplets by stirring, so giving an emulsion. Following the meltemulsification, the resultant electrodeposition coating material wasdiluted further with 1330 parts by weight of deionized water and cooledto room temperature. The dilute electrodeposition coating material wascompletely stable with respect to settling; even after three months ofstorage at room temperature, no sediment was found. Theelectrodeposition coating material had the following characteristics:

[0123] Solids content (1 hour/30° C.): 43% by weight,

[0124] MEQ-base: 0.8 meg/g solid resin,

[0125] MEQ-acid: 0.28 meg/g solid resin,

[0126] pH: 5.8,

[0127] Viscosity: 20 s (DIN 4 cup at 23° C.), and

[0128] z-average particle diameter: 50 to 100 nm.

Example 2 The Preparation of an Electrodeposition Coating Material ofthe Invention by Melt Emulsification

[0129] Example 1 was repeated except that the homogenized melt wasconveyed uniformly into the aqueous medium via an injection tube and theresultant mixture was pumped uniformly into a three-stage toothed-wheeldispersing unit (“K-Generator” from Kinematica AG, Lucerne, Switzerland)and dispersed therein.

[0130] The resultant dilute electrodeposition coating material had thesame advantageous properties as that of Example 1.

Examples 3 and 4 The Use of the Electrodeposition Coating Materials ofthe Invention of Examples 1 and 2 to Produce Electrodeposition Coatings

[0131] For Example 3, an electrodeposition bath comprising 2135 parts byweight of the electrodeposition coating material of Example 1, 603 partsby weight of the pigment paste of Preparation Example 3 and 2263 partsby weight of deionized water was prepared.

[0132] For example 4, an electrodeposition bath comprising 2135 parts byweight of the electrodeposition coating material of Example 2, 603 partsby weight of the pigment paste of Preparation Example 3 and 2263 partsby weight of deionized water was prepared.

[0133] The electrodeposition baths were aged with stirring at roomtemperature for 3 days. Their key performance properties and theconditions of the deposition are compiled in the table. TABLEPerformance properties of the electrodeposition baths and conditions oftheir deposition Example Feature 1 2 pH 5.9 6 Conductivity (mS/cm) 1.91.9 Bath temperature (° C.) 28 28 Removal voltage (V) 350 350 Depositionvoltage (V) 220 220

[0134] The electrodeposition coating films were deposited in the courseof two minutes on zinc-phosphated steel test panels connected ascathodes, which had not been given a subsequent chromium(VI) rinse. Thecoated steel test panels were removed from the electrodeposition baths.The electrodeposition coating films on the panels were rinsed withdeionized water and subsequently baked at 175° C. (panel temperature)for 15 minutes.

[0135] The resultant electrocoatings of Examples 3 and 4 have a dry filmthickness of 22 μm. Their leveling was outstanding. They were completelysolvent-stable and withstood more than 100 double strokes with a cottonpad soaked with methyl ethyl ketone. Their Erichsen cupping was 7 mm.Their corrosion protection effect was outstanding.

What is claimed is:
 1. An electrodeposition coating material preparableby (i) melting at least one self-crosslinking binder, or (ii) separatelymelting at least one externally crosslinking binder and at least onecrosslinking agent and supplying the melts to a mixing unit in which themelts are homogenized, introducing the resultant melt into an aqueousmedium, and emulsifying it therein.
 2. The coating material as claimedin claim 1, wherein the aqueous medium comprises at least oneneutralizing agent.
 3. The coating material as claimed in claim 2,wherein the neutralizing agent is at least one acid.
 4. The coatingmaterial as claimed in any of claims 1 to 3, wherein the mixing unit isa static mixer.
 5. The coating material as claimed in any of claims 1 to4, wherein the melt is emulsified in the aqueous medium in a staticmixer, in a rotor-stator system or in a high-pressure homogenizer. 6.The coating material as claimed in claim 5, wherein a high-pressurehomogenizer is used which operates in accordance with the opposed-jetprinciple.
 7. The coating material as claimed in claim 5, wherein saidrotor-stator system comprises a high-speed stirrer (Ultraturrax), a wetrotor mill, an in-line dissolver, or a toothed-wheel dispersing unit. 8.The coating material as claimed in any of claims 1 to 7, wherein thediscontinuous phase of the emulsion has an average droplet size of 40 to1000 nm.
 9. The use of the coating material as claimed in any of claims1 to 8 to coat electrically conductive substrates.
 10. A process forcoating electrically conductive substrates by electrophoreticallydepositing an electrodeposition coating material on the substrates andthermally curing the resultant electrodeposition coating film alone ortogether with at least one further coating film present thereon, whichcomprises using an electro-deposition coating material as claimed in anyof claims 1 to 8.